Catalyst components for the polymerization of olefins

ABSTRACT

The present invention relates to spherical catalyst components for the polymerization of olefins of formula RCH═CHR, in which R is independently selected from hydrogen or a hydrocarbon group with 1-10 carbon atoms, comprising a homogenous transition metal compound of formula MP x,  in which P is a ligand that is coordinated to the metal and x is the valence of the metal M which is an atom of a transition metal M selected from the Groups 3 to 11 or the lanthanide or actinide groups of the Periodic Table of the Elements (new IUPAC version), said transition metal compound being dispersed in a solid hydrocarbon matrix that has a melting point above 70 ° C.. The said catalyst components are able to give polymers in good yields and spherical morphology.

[0001] The present invention relates to components of catalysts for thepolymerization of olefins and the process for their preparation, thecatalysts obtained from them and the use of the said catalysts in thepolymerization of olefins. Homogeneous catalysts for the polymerizationof olefins obtained from compounds of formula ML_(x) in which M is atransition metal especially Ti, Zr, Hf. Cr, Pd and Ni, L is a ligandthat is coordinated to the metal, and x is the valence of the metal, areknown from the literature. Examples of catalysts of this type with veryhigh activity are those obtained by reacting metallocene compoundsCp₂ZrCl₂ or Cp₂TiCl₂, or their derivatives substituted in thecyclopentadienyl ring, with polyalumoxane compounds containing the—(R)AlO—repeating unit, in which R is preferably methyl (U.S. Pat. No.4,542,199 and EP-A-129368). Catalysts of the aforementioned type inwhich the metallocene compound contains two indenyl or tetrahydroindenylrings with a bridging bond to lower alkylenes or to other divalentradicals are suitable for the preparation of stereoregular polymers ofpropylene and of other alpha olefins (EP-A-185918).

[0002] Stereospecific catalysts are also obtained fromdicyclopentadienyl compounds in which the two rings are substituted invarious ways with groups with steric hindrance such as to impede therotation of the rings about the axis with the metal. The substitution ofthe cyclopentadienyl ring of indenyl or tetrahydroindenyl in suitablepositions supplies catalysts that are endowed with very highstereospecificity (EP-A-485823, EP-A-485820, EP-A-519237, U.S. Pat. No.5,132,262 and U.S. Pat. No. 5,162,278). The catalysts described abovesupply polymers with very narrow molecular weight distribution (Mw/Mn ofabout 2).

[0003] Furthermore, some of these catalysts have the property of formingcopolymers of ethylene with alpha olefins of the LLDPE type orelastomeric ethylene/propylene copolymers with very uniform distributionof the comonomenic units. The LLDPE polyethylene obtained is furthercharacterized by low solubility in solvents such as xylene or n-decane.

[0004] The polypropylene obtained with the more stereospecific catalystsmentioned above exhibits greater crystallinity and a higher distortiontemperature relative to the polymer obtainable with the conventionalheterogeneous Ziegler-Natta catalysts.

[0005] Homogeneous catalysts with a different structure are described ininternational patent application WO 96/23010. These catalysts,comprising a complex between a transition metal and at least onebidentate ligand that has a particular structure, are capable ofpolymerizing olefins to give a wide range of polymers includingcopolymers comprising olefins and polar monomers such as carbonmonoxide, vinylacetate, (meta)acrylates etc.

[0006] Despite their excellent properties in terms of quality of thepolymeric products, considerable difficulties are encountered when saidhomogeneous catalysts are to be used in industrial processes ofproduction of polyolefins that are not carried out in solution. Thehomogeneous catalysts in fact, are not able to provide polymers with aregular morphology when used in processes such as polymerization ingas-phase. In order to make it possible their use in non-solutionpolymerization processes, the homogeneous catalysts have to be madeheterogeneous by supporting them on suitable supports that are able toendow the catalyst with appropriate morphological properties. Variouskinds of supports can be used for this purpose including, among others,metal oxides such as silica, magnesium halides or polymeric supportssuch as polyethylene, polypropylene and polystyrene. A characteristicthat is common to these supports is that they are porous and so enablethe metallocene compound to be fixed by being deposited in the pores.The catalytic components thus obtained are therefore in the form ofparticles of inert material, organic or inorganic, carrying in thesurface layer, in correspondence of the pores, the transition metalcompound that constitutes one of the components of the catalyst. Toachieve efficient support, however, the porosity of the support must beaccurately controlled. Moreover, since the extent of supportationdepends mainly on the porosity of the support particles, it also provesvery difficult to achieve homogeneous distribution of the quantity ofcompound supported because the individual support particles or fractionshave differences in porosity that are sometimes very considerable. Inany case, the upper limit of the amount of transition metal compoundthat can be supported is always determined by the porosity of thesupport. For example, U.S. Pat. No. 5,106,804 describes catalystscomprising a metallocene compound supported on MgCl₂ in spherical formand partially complexed with an electron-donor compound in which theamount of Zr compound supported on MgCl₂ is relatively low (the Zr/Mgratio in the catalyst is less than about 0.05). Furthermore, thepolymerization yields are not such as to make it possible to obtainpolymers containing sufficiently low residues of the catalyst. It is infact known that supporting tends to lower the activity of homogeneouscatalysts considerably. European patent EP 798315 describes a method ofpreparing homogeneous mixtures consisting of a metallocene, a cocatalystand a dispersing medium having a oily or waxy consistency that isselected among the non-aromatic long-chain hydrocarbons that haveboiling point above 150° C. and viscosity of at least 1 Pa.s at 25° C.According to the inventors these mixtures are endowed with improvedstability. Although included in the generic description, the use of aspecific hydrocarbon matrix with a melting point above 70° C. as adispersing medium it is never described specifically. Nor, moreover,there is any specific description of a solid catalytic component inspherical form that comprises a homogeneous catalyst dispersed within asolid hydrocarbon matrix at room temperature. The only use of a soliddispersing medium is reported in Example 3 describing the preparation ofsolid mass of a paraffinic wax having a melting point between 65 and 70°C. and containing methyl alumoxane in an amount equal to approx. 66 wt.%, which has then been mechanically comminuted to a fine grain powder.In addition to the fact that these mixtures do not possess a suitablemorphology, it is also important to observe that according to Table 1 ofthe said application, the metallocene compound is not present in theformulation of example 3. As it can be seen from the polymerizationdata, however, the yields that are obtained using this catalyst are verylow even if further alumoxane is added in the reactor. Internationalpatent application WO 96/34020 describes a method of preparation of asolid catalyst that comprises supporting a metallocene and an activatoron a support, preferably porous, and then coating the said supportedcatalyst with an inert organic material that is preferably a hydrocarboncomponent of molecular weight between 200 and 20 000 and is soluble inaromatic solvents at temperatures above 70° C. According to the saidpatent application, the catalyst thus prepared makes it possible toovercome the problem of reactor fouling, but the polymerization yields(expressed in terms of kg of polymer per g of transition metal) are verylow. Surprisingly, it was found that the solid components of catalystsobtained by dispersing a homogeneous catalyst within a hydrocarbonmatrix possessing certain characteristics are capable of formingcatalysts that have high activity and are able to produce polymers withexcellent morphological properties. An object of the present inventiontherefore comprises spherical catalyst components for the polymerizationof formula RCH═CHR, in which R is independently selected from hydrogenor a hydrocarbon group with 1-10 carbon atoms, comprising a homogeneoustransition metal compound of formula MP_(x), in which P is a ligand thatis coordinated to the metal and x is the valence of the metal M which isan atom selected from the Groups 3 to 11 or the lanthanide or actinidegroups of the Periodic Table of the Elements (new IUPAC version), saidtransition metal compound being dispersed in a solid hydrocarbon matrixthat has a melting point above 70° C. Hydrocarbon matrices with amelting point above 80° C. are particularly preferred, and even morepreferably above 90° C. The said matrix is preferably selected from thegroup comprising solid paraffinic waxes, polyolefins or their mixtures.The use of solid paraffinic waxes is particularly preferred.

[0007] Preferably, moreover, the said matrix, in contrast to thesupports commonly employed in this technology, is characterized by verylow porosity. In particular the porosity, measured by the mercurymethod, is less than 0.3 cm³/g and preferably below 0.15 cm³/g. Thesolid paraffinic waxes are generally indicated as the products that arederived from the fraction of lubricating oils that is in its turnobtained by fractional distillation of crude oil. When this fraction iscooled the waxes separate from the oils and are deposited as solidproducts, which are then recovered by filtration. From the chemicalstandpoint, the waxes are mixtures comprising straight-chain,branched-chain or cyclic hydrocarbons. The polyolefins that can be usedas solid matrix of the present invention comprise the polyolefins.generally known in the art such as (co)polymers of ethylene (HDPE,LLDPE), of propylene (isotactic, atactic and syndiotactic homopolymericpolypropylene, random copolymers with ethylene, butene-1, hexene-1 ortheir mixtures) of butene as well as polyolefins obtained by thepolymerization of vinylaromatic monomers such as styrene,divinylbenzene, etc. Among the polyolefins that can be used according tothe present invention, the preferred ones are the (co)polymers ofethylene of low and very low molecular weight (i.e. those having anintrinsic viscosity lower than 5 and preferably comprised between 0.1and 4), the ethylene copolymers that have a percentage by weight ofcomonomer greater than 10%, the highly modified copolymers of propyleneand the elastomeric ethylene-α-olefin copolymers possibly containingminor proportions of diene or polyene. As is well known, the saidpolymers can be obtained for example by polymerization of the startingolefins carried out in the presence of catalysts of the Ziegler-Nattatype comprising the product of reaction between an organo-metalliccompound and a transition metal compound preferably selected from Ti orV. As described previously, the catalyst components of the inventioncomprise a compound containing a transition metal M selected from theGroups 3 to 11 or the lanthanide or actinide groups of the PeriodicTable of the Elements (new IUPAC version). In particular, in the saidcompound the transition metal is preferably selected among Ti, V, Zr,Hf, Sc, Cr, Fe, Co, Ni, and Pd. In one of the preferred embodiments, thesaid transition metal compound is selected among the compounds offormula (I)

QL₁ZMX¹ _(p)   (I)

[0008] wherein Q is selected from substituted or unsubstitutedcyclopentadienyl radicals, which can carry one or more condensed cycles,which can contain heteroatoms; such as indenyl, tetrahydroindenyl,fluorenyl, octaidrofluorenyl, tetrahydrofluorenyl, indolyl, thiopenthyl,dithiophenecyclopentadienyl;

[0009] Z has the same meaning of Q and it can also be ═NR^(8,) —O—, —S—and ═PR⁸, R⁸ being selected from hydrogen, a C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl, C₂-C₂₀-alkenyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl orC₇-C₂₀-ary-alkyl radical which can contain a heteroatom;

[0010] L is a divalent bridge connecting the moieties Q and Zpreferebaly it is selected from the group consisting ofC₁-C₂₀-alkylidene, C₃-C₂₀-cycloalkylidene, C₂-C₂₀-alkenylidene,C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene or C₇-C₂₀-aryalkylidene radicalwhich can contain a heteroatom; more preferably L is selected from thegroup consisting of CR³ ₂, C₂R³ ₄, SiR³ ₂, Si₂R³ ₄ o CR³ ₂ SiR³ ₂wherein R3 is selected from the group consisting of from hydrogen, aC₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₂-C₂₀-alkenyl, C₆-C₂₀-aryl,C₇-C₂₀-ary-alkyl radical which can contain a heteroatom; preferably R³is hydrogen, methyl, phenyl;

[0011] M is an atom of a transition metal M selected from the Groups 3to 10 or the lanthanide or actinide groups of the Periodic Table of theElements (new IUPAC version), X¹, same or different, is a ligandselected from hydrogen, a halogen, R⁹, OR⁹, OSO₂CF₃, OCOR⁹, SR⁹, NR⁹ ₂or PR⁹ ₂ group, wherein R⁹ is selected from hydrogen, a C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl, C₂-C₂₀-alkenyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl orC₇-C₂₀-arylalkyl radical, optionally containing a heteroatom; p is aninteger of from 0 to 3, preferably from 1 to 3, more preferably p is 2,being equal to the oxidation state of the metal M minus 2 1 is 0 or 1;Non-limiting examples of compounds of formula (I) are those described inWO 98/22486, WO 99/58539 WO 99/24446, U.S. Pat. No. 5,556,928, WO96/22995 EP-485822 and EP-485420. Another class of preferred catalystsis that comprising late transition metal complexes corresponding toformula (II) or (III):

LMX_(p)X′_(s)   (II)

LMA   (III)

[0012] wherein M is a metal belonging to Group 8, 9, 10 or 11 of thePeriodic Table of the Elements (new IUPAC notation);

[0013] L is a bidentate or tridentate ligand of formula (IV):

[0014] wherein:

[0015] B is a C₁-C₅₀ bridging group linking E¹ and E², optionallycontaining one or more atoms belonging to Groups 13-17 of the PeriodicTable;

[0016] E¹ and E², the same or different from each other, are elementsbelonging to Group 15 or 16 of the Periodic Table and are bonded to saidmetal M;

[0017] the substituents R¹, the same or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₁-C₂₀ alkyliden, C₃-C₂₀cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals,optionally containing one or more atoms belonging to groups 13-17 of thePeriodic Table of the Elements (such as B, Al, Si, Ge, N, P, O, S, F andCl atoms); or two R¹ substituents attached to the same atom E¹ or E²form a saturated, unsaturated or aromatic C₄-C₈ ring, having from 4 to20 carbon atoms; m and n are independently 0, 1 or 2, depending on thevalence of E¹ and E², so to satisfy the valence number of E¹ and E²; qis the charge of the bidentate or tridentate ligand so that theoxidation state of MX_(p)X′_(s) or MA is satisfied, and the compound(II) or (m) is overall neutral;

[0018] X, the same or different from each other, are monoanionic sigmaligands selected from the group consisting of hydrogen, halogen, —R,—OR, —OSO₂CF₃, —OCOR, —SR, —NR₂ and —PR₂ groups, wherein the Rsubstituents are linear or branched, saturated or unsaturated, C₁-C₂₀alky, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀arylalkyl radicals, optionally containing one or more atoms belonging togroups 13-17 of the Periodic Table of the Elements (new IUPAC notation),such as B, N, P, Al, Si, Ge, O, S and F atoms; or two X groups form ametallacycle ring containing from 3 to 20 carbon atoms; the substituentsX are preferably the same; X′ is a coordinating ligand selected frommono-olefins and neutral Lewis bases wherein the coordinating atom is N,P, O or S; p is an integer ranging from 0 to 3, so that the finalcompound (II ) or (Ill) is overall neutral; s ranges from 0 to 3; and Ais a π-allyl or a π-benzyl group.

[0019] According to a preferred embodiment of the present invention, thebridging group B corresponds to a structural formula selected from thegroup consisting of:

[0020] wherein G is an element belonging to Group 14 of the PeriodicTable, and is preferably C, Si or Ge; r is an integer ranging from 1 to5; E³ is an element belonging to Group 16 and E⁴ is an element belongingto Group 13 or 15 of the Periodic Table; the substituents R², the sameor different from each other, are selected from the group consisting ofhydrogen, linear or branched, saturated or unsaturated C₁-C₂₀ alkyl,C₁-C₂₀ alkoxy, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl andC₇-C₂₀ arylalkyl radicals, optionally containing one or more atomsbelonging to groups 13-17 of the Periodic Table (such as B, Al, Si, Ge,N, P, O, S, F and Cl atoms); or two R² substituents form a saturated,unsaturated or aromatic C₄-C₈ ring, having from 4 to 20 carbon atoms, orthey form a polycyclic ring system, optionally containing one or moreGroup 13-16 elements; a substituent R¹ and a substituent R² may form asubstituted or unsubstituted, saturated, unsaturated or aromatic C₄-C₈ring, having from 4 to 20 carbon atoms and optionally containing one ormore Group 13-16 element.

[0021] In the bidentate or tridentate ligand L of formula (IV), E^(l)and E² belong to Group 15 or 16 of the Periodic Table, and preferablyare selected from the group consisting of N, P, O, and S. In the latetransition metal compounds of formula (II) or (III), the substituentsR¹, the same or different from each other, are preferably bulky groups;more preferably, they are C₆-C₂₀ aryl groups, and even more preferablyare substituted in the 2 and 6 positions with a C₁-C₁₀ alkyl group. Thesubstituents X are preferably hydrogen, methyl, phenyl, Cl, Br or I; pis preferably 1, 2 or 3. When X′ is a neutral Lewis base wherein thecoordinating atom is N, P, O or S, it is preferably selected from thegroup consisting of phosphines, amines, pyridines, nitriles, sulfidesand ethers; even more preferably, it is selected from the groupconsisting of triphenylphosphine, tri(C₁-C₆ alkyl)phosphines,tricycloalkyl phosphines, diphenyl allyl phosphines, dialkyl phenylphosphines, triphenoxyphosphine, pyridine, di(C₁-C₃ alkyl) ether,tetrahydrofuran and nitriles, especially acetonitrile.

[0022] When X′ is a mono-olefin, it is a hydrocarbyl group having onecarbon-carbon double bond, having from 2 to 20 carbon atoms; preferablyis a substituted or unsubstituted C₂-C₆ alkene. The variable s ispreferably 0 or 1. A is π-allyl or a π-benzyl group.

[0023] By a π-allyl group is meant a monoanionic ligand with 3 adjacentsp² carbon atoms bound to a metal center in an Θ³ fashion. The three sp²carbon atoms may be substituted with other hydrocarbyl groups orfunctional groups. Typical π-allyl groups include:

[0024] wherein R is hydrocarbyl.

[0025] By a π-benzyl group is meant π-allyl ligand in which two of thesp² carbon atoms are part of an aromatic ring. Typical π-benzyl groupsinclude:

[0026] and

[0027] The quantity of transition metal compound present in thecomponent of the present invention can vary over a wide range. Generallythe said quantity varies between 0.01 and 50 wt. % relative to the totalweight of the component, preferably between 0.5 and 25% and morepreferably between 1 and 10%. In particular, when the transition metalcompound is selected from among the compounds of formula (I) itsquantity is preferably between 1 and 6%. As already mentioned, thecomponents of the invention form, with one or more compounds capable ofactivating the transition metal compound, catalysts that areparticularly suitable for the polymerization of olefins. A class ofactivator compounds that are particularly preferred comprisesorganometallic compounds of aluminium. Particularly preferred are thealumoxanes and/or a compound able to form an alkylmetal cation. Suitableactivating agents are linear alumoxanes having formula:

[0028] wherein the R¹⁷ substituents, the same or different from eachother, are selected from the group consisting of hydrogen, linear orbranched, saturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl,C₆-C₂₀-aryl, C7-C20-alkylaryl and C₇-C₂₀-arylalkyl radicals, optionallycontaining Si or Ge atoms; and t is an integer ranging from 0 to 40 andR¹⁷ has the meaning reported above; or cyclic alumoxanes having formula:

[0029] wherein t is an integer ranging from 2 to 40 and R¹⁷ has themeaning reported above.

[0030] Examples of alumoxanes suitable as activating cocatalysts in thecatalysts system according to the present invention are methylalumoxane(MAO), 2,4,4-trimethyl-pentylalumoxane (TIOAO), 2-methyl-pentylalumoxaneand 2,3-dimenthyl-butylalumoxane. Mixtures of different alumoxanes canalso be used. Activating cocatalysts suitable as component (B) in thecatalysts of the invention are also the product of the reaction betweenwater and an organometallic aluminum compound; particularly suitable arethe organometallic aluminum compounds described in the European patentapplication EP 0 575 875 (formula (II)) and in the international patentapplications WO 96/02580 (formula (II)), WO 99/21899 (formula (II)) andin the European patent application no. 99203110.4 (formula (II)).Non-limiting examples of organometallic aluminum compounds are:

[0031] tris(methyl)aluminum, tris(isobutyl)aluminum,

[0032] tris(2,4,4-trimethyl-pentyl)aluminum bis(isobutyl)aluminumhydride,

[0033] bis(2,4,4-trimethylpentyl)aluminum hydrideisobutyl-bis(2,4,4-trimethyl-pentyl)aluminum

[0034] tris(2,3-dimethyl-hexyl)aluminumtris(2,3,3-trimethyl-butyl)aluminum

[0035] tris(2,3-dimethyl-butyl)aluminumtris(2,3-dimethyl-pentyl)aluminum

[0036] tris(2-methyl-3-ethyl-pentyl)aluminumtris(2-ethyl-3-methyl-butyl)aluminum

[0037] tris(2-ethyl-3-methyl-pentyl)aluminumtris(2-isopropyl-3-methyl-butyl)aluminum

[0038] tris(2,4-dimethyl-heptyl)aluminum tris(2-phenyl-propyl)aluminium

[0039] tris[2-(4-fluoro-phenyl)-propyl]aluminiumtris[2-(4-chloro-phenyl)-propyl]aluminium

[0040] tris[2-(3-isopropyl-phenyl)-propyl]aluminiumtris(2-phenyl-butyl)aluminium

[0041] tris(3-methyl-2-phenyl-butyl)aluminiumtris(2-phenyl-pentyl)aluminium

[0042] tris[2-(pentafluorophenyl)-propyl]alumniniumtris[2,2-diphenyl-ethyl]aluminium and

[0043] tris[2-phenyl-2-methyl-propyl]aluminium.

[0044] Mixtures of different organometallic aluminum compounds and/oralumoxanes can also be used. The molar ratio between aluminum and themetal M of the bridged metallocene compound is preferably comprisedbetween 10:1 and 50,000:1, and more preferably between 100:1 and4,000:1. Further alumoxanes suitable as activating agents in the processof the present invention are alkylhaloaluminoxanes, as described in theInternational Patent Application WO 00/22007, and in particular1,3-dichloro-1,3-diethyldialuminoxane [EtAlCl]₂O and1,3-dichloro-1,3-diisobutylaluminoxane [iBuAlCl]₂O. Other compoundscapable of activating the transition metal compounds describedpreviously are the compounds able to form an alkylmetallocene cation;preferably said compounds have formula Y⁺Z⁻, wherein Y⁺ is a Brønstedacid, able to donate a proton and to react irreversibly with asubstituent X of the metallocene compound of formula (I), and Z³¹ is acompatible non-coordinating coordinating anion, able to stabilize theactive catalytic species which results from the reaction of the twocompounds and which is sufficiently labile to be displaceable by anolefin substrate. Preferably, the anion Z⁻ consists of one or more boronatoms. More preferably, the anion Z³¹ is an anion of the formula BAr₄⁽⁻⁾, wherein the substituents Ar, the same or different from each other,are aryl radicals such as phenyl, pentafluorophenyl orbis(trifluoromethyl)phenyl. Tetrakis-pentafluorophenyl borate isparticularly preferred. Other useful non-coordinating anions Z⁻ can beSbF₆ ⁻, PF₆ ⁻, BF₄ ⁻, trifluoromethanesulphonate andp-toluenesulphonate. Moreover, neutral Lewis acids such as BAr₃, SbF₅and BF₃ can conveniently be used. The solid components according to thepresent invention can be prepared by a process comprising (a) dispersinga homogeneous transition metal compound according one or more offormulae (I)-(III) above, in a hydrocarbon matrix having a melting pointabove 70° C. which has been brought in a liquid form and (b) solidifyingthe said matrix, containing the said transition metal compound, in theform of spherical particles.

[0045] According to a particular embodiment the transition metalcompound is dispersed, with the aid of a mixer, in the moltenhydrocarbon matrix and the mixture thus obtained is sprayed undertemperature conditions such as to cause immediate solidification of thedroplets as spherical particles. The conditions under which spraying andinmmediate cooling take place (flow rate and pressure of the carrier gasand its ratio to the quantity of mixture to be sprayed; flow rate,pressure and temperature of the cooling gas) can be properly selectedaccording to the knowledge of the skilled in the art, in order to obtainaverage diameters of the solid particles over quite a wide range. Inparticular the solid particles that constitute the solid components ofthe present invention have a spherical morphology and dimensions between1 and 400 μm and preferably between 10 and 300 μm. The term sphericalmorphology means, according to the present invention, particlespossessing a ratio between maximum diameter and minimum diameter of lessthan 1.5 and preferably less than 1.3.

[0046] Before being dispersed in the matrix the transition metalcompound is preferably dissolved with a minimum amount of solvent. Forthis purpose it is possible to use any inert hydrocarbon medium in whichthe transition metal compound is soluble, for example toluene, benzeneand similar hydrocarbons. In particular, whenever possible, it ispreferable to use a hydrocarbon solvent that has a boiling point below120° C. so as to facilitate its removal from the final product. The useof a low boiling solvent assisting both the dispersion of the transitionmetal compound and the availability of the hydrocarbon matrix in liquidform is particularly preferred when the transition metal compound candecompose at temperatures at which the hydrocarbon matrix melts inabsence of solvent. In this case the concomitant use of a solvent whichis able to at least partially solubilize the matrix can allow to lowerthe temperature at which the hydrocarbon matrix/solvent system becomessufficiently and homogeneously liquid to permit the dispersion of thetransition metal compound. In a particular aspect of the presentinvention, the solution of the said transition metal compound is broughtinto contact with the matrix in the solid state which is then melted,while stirring. In particular, excellent results have been obtained bydissolving, together with the transition metal compound, also theactivator component for example AlEt₂Cl (DEAC) or a polyalkyl-alumoxaneof the type previously described, and in particular MAO or its mixtureswith an Al-alkyl compound, using molar ratios of alkyl-Alcompound/transition metal compound greater than 2, preferably between 5and 500. The solutions that are obtained are in fact particularlysuitable for providing components of catalysts that have high activity.An alternative method of preparation of the components of the inventioncomprises:

[0047] (i) feeding the hydrocarbon matrix and the transition metalcompound, possibly precontacted with the activator compound, into anextruder;

[0048] (ii) extruding the said mixture in the form of filaments and

[0049] (iii) cutting the said filaments before they have solidifiedcompletely, obtaining discrete particles. The catalysts of the presentinvention have wide applications. In particular they can be used in allthe olefin polymerization processes in which said transition metalcompound catalysts are normally employed. For example, they can be usedin the (co)polymerization of olefins of the type CH₂═CHR or of the typeRCH═CHR in which R is an hydrocarbon radical with 1-10 carbon atoms, ofcyclic olefins and diene or polyene monomers. Furthermore, they can beused in the (co)polymerization of CH₂═CHR olefins with polar monomerssuch as carbon monoxide, vinylacetate, maleic anhydride, halogenatedolefins, for the preparation of modified polyolefins such asethylene-vinylacetate (EVA) copolymers, copolymers of ethylene orpropylene with maleic anhydride, or copolymers of ethylene and carbonmonoxide (polyketones).

[0050] In particular the catalysts obtained from compounds of the typeC₂H₄(Ind)₂ZrCl₂, C₂H₄(H₄Ind)ZrCl₂ and Me₂Si(Me₄Cp)₂ZrCl₂ are suitablefor production of LLPDE (copolymers of ethylene containing smallerproportions, generally less than 20 mol. %, of C₃-C₁₂ alpha olefin)characterized by relatively low values of density relative to thecontent of alpha olefin, by reduced solubility in xylene at roomtemperature (less than approx. 10 wt. %) and by molecular weightdistribution Mw/Mn between about 2.5 and 5.

[0051] The catalysts of the present invention can be used in thepolymerization of olefins either carried out in the liquid phase, suchas solution or suspension, or in gas-phase processes. In particular theuse of the catalysts of the invention in the gas-phase processes isespecially preferred as it makes it possible to obtain polymers thathave good morphological properties. The said gas-phase process can becarried out working in one or more fluidized-bed or mechanically-stirredreactors. Polymerization is generally carried out at temperaturesbetween 40 and 120° C., preferably between 50 and 90° C. When working inthe gas phase, the working pressure is generally between 0.5 and 10 MPa,preferably between 1 and 2 MPa. Hydrogen or other compounds known in theart having the same function can be used as molecular weight regulators.Moreover, it is possible, prior to polymerization, to carry out a stageof pre-polymerization such as to make the said catalyst particularlysuitable for the next polymerization stage. The pre-polymelization stageis particularly recommended whenever a solid hydrocarbon matrix is usedthat has a melting point below the temperature of the polymerizationstage. In this case it is particularly preferred to carry outpre-polymerization at temperatures below the melting point of thehydrocarbon matrix with the aim of avoiding the loss of morphologicalproperties owing to melting of the hydrocarbon matrix in the reactor. Inthis case the pre-polymerization is carried out in particular attemperatures between −10 and 70° C. and preferably at temperaturesbetween 0 and 50° C. In general, the pre-polymerization can be carriedout in the liquid phase, comprising an inert hydrocarbon solvent such aspropane, hexane, heptane, isobutane or a monomer, or in the gas phaseworking at temperatures generally below 100° C., preferably between 20and 70° C. As explained above, the prepolymerization in gas-phase isespecially preferred because it allows to preserve the morphology of thecatalysts component. The pre-polymerization is carried out bypolymerizing small amounts of monomer for the time necessary to obtainquantities of polymer between 0.5 g and 2000 g per g of solid component,preferably between 5 and 500 g per g of solid component and morepreferably between 10 and 100 g per gram of solid component. Preferably,pre-polymerization is carried out with ethylene, propylene or theirmixtures. The pre-polymerized catalyst thus obtained is then used in thenext polymerization stage. The process for the polymerization of olefinsaccording to the invention can be carried out in the liquid phase in thepresence or absence of an inert hydrocarbon solvent, or in the gasphase. The hydrocarbon solvent can either be aromatic such as toluene,or aliphatic such as propane, hexane, heptane, isobutane or cyclohexane.The polymerization temperature is generally comprised between −100° C.and +100° C. and, particularly between 10° C. and +90° C. Thepolymerization pressure is generally comprised between 0,5 and 100 bar.

[0052] The following examples are given by way of illustration of theinvention and are non-limiting. The properties indicated are determinedaccording to the following methods:

[0053] Size of the Catalyst Particles

[0054] is determined by a method based on the principle of the opticaldiffraction of monochromatic laser light with the “Malvern Instr. 2600”apparatus. The average size is given as P50.

[0055] INTRINSIC VISCOSITY [η] is determined in tetraline at 135° C.

EXAMPLES Example 1

[0056] 10 g of TIBAO (300 g/l solution in cyclohexane) and 310 mg ofrac-ethylene-bis-(dimethyl-indenyl)-zirconium dichloride arepre-contacted for 5 minutes at room temperature in a glass flaskpreviously treated with N₂. 15 g of a paraffinic wax with melting pointof 105-110° C. (Lubriol C109) is added to the solution thus obtained.The suspension is kept stirred and is heated to a temperature of 100°C., and connected to a vacuum pump to remove the solvent. When boilingis no longer observed, the temperature is raised again to 120° C.,obtaining a homogeneous liquid phase of a yellowish-brown colour. Themelt thus obtained is transferred to the jacketed vessel, heated to 130°C., that supplies the sprayer. The molten mixture is then sprayed inconditions such as to obtain spheres with average diameter of 180 μm andwith the following composition: Zr=0.18%; Al=5.8%.

Example 2

[0057] In a glass flask treated with N₂, 3.8 g of triisooctyl aluminium(TIOA) is pre-contacted with 24 cm³ of a solution of methyl alumoxane(MAO) at 10% in toluene and they are left to react for 20 min at roomtemperature. 240 mg of rac-ethylene-bis-(dimethyl-indenyl)-zirconiumdichloride is added to this mixture and they are left to pre-contact for10 minutes at room temperature. 9.9 g of a paraffinic wax with a meltingpoint of 105-110° C. (Lubriol C109) is added to the solution thusobtained. The suspension is kept stirred and is heated to a temperatureof 100° C., and is connected to a vacuum pump to remove the solvent.When boiling is no longer observed, the temperature is raised again to120° C., obtaining a homogeneous liquid phase of a yellowish-browncolour. The melt thus obtained is transferred to the jacketed vessel,heated to 130° C., which supplies the sprayer. The molten mixture isthen sprayed, collecting the droplets in an N₂ atmosphere at atemperature of approx. 10° C. to speed up the solidification of thedroplets. Spheres are collected having average diameter of 100 μm andthe following composition: Zr=0.29%; Al=8.68%.

Example 3

[0058] Polymerization of Ethylene

[0059] A 4L stainless-steel reactor, equipped with a thermosettingjacket ,a magnetic stirrer pressure indicator, temperature indicatorfeed line for monomer equipped with a thermal mass flowmeter to measurethe ethylene uptake is used. 1600 ml of hexane is loaded into thereactor at approximately 30° C., followed by 0.2 g of tri-isobutylaluminum as the scavenger. The polymerization is started by injecting670 mg of the catalyst prepared as in Example 1 by means of nitrogenoverpressure. The reactor temperature is increased up to 70 ° C. in10-15 minutes. At 70° C. ethylene is continuously fed to maintain apressure of 10 barg. The polymerization is stopped after 2 hours byventing and cooling the reactor: The polymer suspension discharged isdried in an oven at 80° C. under nitrogen atmosphere. 300 g of polymeris obtained with intrinsic viscosity [η]=3.15 dL/g for a yield of 170kgPE/g Zr.

Example 4

[0060] A fluidized bed reactor equipped with a compressor tore-circulate the gas to the reactor after passing though a heatexchanger unit was used. The equipment is provided with a smallpre-polymerization vessel connected to the gas phase reactor.. 600 mg ofthe catalyst prepared as in example 2 was loaded in the 0.5Lpre-polymerization reactor equipped with a stirrer and previously purgedwith propane and TIBA as scavenger at 90° C. for 2 hours. Thepre-polymerization was carried out in slurry at 30° C. in 0.3L of liquidpropane and 30 g of ethylene. After 30 minutes the slurry wastransferred to the fluidized bed to continue the polymerization in gasphase at 70° C. and 12 bar of ethylene partial pressure. After 4 hoursof polymerization the reactor was cooled and vented and the polymerrecovered. 120 g of spherical particles were obtained for an activity of200 g PE/g cat and with a bulk density of 0.289 g/cc . The I.V. of thepolyethylene produced was 9.86 dL/g.

1. Spherical catalyst components for the polymerization of olefins offormula RCH═CHR, in which R is independently selected from hydrogen or ahydrocarbon group with 1-10 carbon atoms, comprising a homogeneoustransition metal compound of formula MP_(x), in which P is a ligand thatis coordinated to the metal and x is the valence of the metal M which isan atom of a transition metal M selected from the Groups 3 to 11 or thelanthariide or actinide groups of the Periodic Table of the Elements(new IUPAC version), said transition metal compound being dispersed in asolid hydrocarbon matrix that has a melting point above 70° C. 2.Spherical catalyst components according to claim 1, in which the solidhydrocarbon matrix has a melting point above 80° C.
 3. Sphericalcatalyst components according to claim 2, in which the solid hydrocarbonmatrix has a melting point above 90° C.
 4. Spherical catalyst componentsaccording to claim 1, in which the solid hydrocarbon matrix is a solidparaffinic wax, a polyolefin or their mixtures.
 5. Spherical catalystcomponents according to claim 4, in which the solid hydrocarbon matrixis a paraffinic wax characterized by a melting point above 80° C. 6.Spherical catalyst components according to any one of the claims from 1to 5, in which the transition metal compound formula (I) QL₁ZMX¹ _(p)  (I) wherein Q is selected from substituted or unsubstitutedcyclopentadienyl radicals, which can carry one or more condensed cycles,which can contain heteroatoms; such as indenyl, tetrahydroindenyl,fluorenyl, octaidrofluorenyl, tetrahydrofluorenyl, indolyl, thiopenthyl,dithiophenecyclopentadienyl; Z has the same meaning of Q and it can alsobe ═NR⁸,—O—,—S—and ═PR⁸, R⁸ being selected from hydrogen, aC₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₂-C₂₀-alkenyl, C₆-C₂₀-aryl,C₇-C₂₀-alkylaryl or C₇-C₂₀-aryalkyl radical which can contain aheteroatom; L is a divalent bridge connecting the moieties Q and Zpreferably it is selected from the group consisting ofC₁-C₂₀-alkylidene, C₃-C₂₀-cycloalkylidene, C₂-C₂₀-alkenylidene,C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene or C₇-C₂₀-aryalkylidene radicalwhich can contain a heteroatom; more preferably L is selected from tegroup consisting of CR³ ₂, C₂R³ ₄, SiR³ ₂, Si₂R³ ₄ o CR³ ₂SiR³ ₂ whereinR3 is selected from the group consisting of from hydrogen, aC₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₂-C₂₀-alkenyl, C₆-C₂₀-aryl,C₇-C₂₀-alkylaryl or C₇-C₂₀-aryalky1 radical which can contain aheteroatom; preferably R³ is hydrogen, methyl, phenyl; M is an atom of atransition metal M selected from the Groups 3 to 10 or the lanthanide oractinide groups of the Periodic Table of the Elements (new IUPACversion), X¹, same or different, is a ligand selected from hydrogen, ahalogen, R⁹, OR⁹, OSO₂CF₃, OCOR⁹, SR⁹, NR⁹ ₂ or PR⁹ ₂ group, wherein R⁹is selected from hydrogen, a C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl,C₂-C₂₀-alkenyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkylradical, optionally containing a heteroatom; p is an integer of from 0to 3, preferably from 1 to 3, more preferably p is 2, being equal to theoxidation state of the metal M minus 2; 1 is 0 or
 1. 7. Sphericalcatalyst components according to claims 1-5, in which the transitionmetal compound is a late transition metal complexes corresponding to theformula (II) or (III): LMX_(p)X′_(s)   (II) LMA   (III) wherein M is ametal belonging to Group 8, 9, 10 or 11 of the Periodic Table of theElements (new KTPAC notation); L is a bidentate or tridentate ligand offormula (IV):

wherein: B is a C₁-C₅₀ bridging group linking E¹ and E², optionallycontaining one or more atoms belonging to Groups 13-17 of the PeriodicTable; E¹ and E², the same or different from each other, are elementsbelonging to Group 15 or 16 of the Periodic Table and are bonded to saidmetal M; the substituents R¹, the same or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₁-C₂₀ alkyliden, C₃-C₂₀cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals,optionally containing one or more atoms belonging to groups 13-17 of thePeriodic Table of the Elements (such as B, Al, Si, Ge, N, P, O, S, F andCl atoms); or two R¹ substituents attached to the same atom E¹ or E²form a saturated, unsaturated or aromatic C₄-C₈ring, having from 4 to 20carbon atoms; m and n are independently 0, 1 or 2, depending on thevalence of E¹ and E², so to satisfy the valence number of E¹ and E²; qis the charge of the bidentate or tridentate ligand so that theoxidation state of MX_(p)X′_(s) or MA is satisfied, and the compound(II) or (III) is overall neutral; X, the same or different from eachother, are monoanionic sigma ligands selected from the group consistingof hydrogen, halogen, —R, —OR, —OSO₂CF₃, —OCOR, —SR, —NR₂ and —PR₂groups, wherein the R substituents are linear or branched, saturated orunsaturated, C₁-C₂₀ alky, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl or C₇C₂₀ arylalkyl radicals, optionally containing one or moreatoms belonging to groups 13-17 of the Periodic Table of the Elements(new IUPAC notation), such as B, N, P, Al, Si, Ge, O, S and F atoms; ortwo X groups form a metallacycle ring containing from 3 to 20 carbonatoms; the substituents X are preferably the same; X′ is a coordinatingligand selected from mono-olefins and neutral Lewis bases wherein thecoordinating atom is N, P, O or S; p is an integer ranging from 0 to 3,so that the final compound (II) or (III) is overall neutral; s rangesfrom 0 to 3; and A is a π-allyl or a π-benzyl group.
 8. Catalysts forthe (co)polymerization of olefins formula RCH═CHR, in which R isindependently selected from hydrogen or a hydrocarbon group with 1-10carbon atoms, comprising the product of reaction between (i) a sphericalcatalyst component comprising a homogeneous transition metal compound offormula MP_(x), in which P is a ligand that is coordinated to the metaland x is the valence of the metal M which is an atom of a transitionmetal M selected from the Groups 3 to 11 or the lanthanide or actinidegroups of the Periodic Table of the Elements (new IUPAC version), saidtransition metal compound being dispersed in a solid hydrocarbon matrixthat has a melting point above 70° C. and (ii) one or more activatorcompounds.
 9. Catalysts according to claim 8, in which the activatorcompound is an organometallic compound of aluminium.
 10. Catalystsaccording to claim 9, in which the activator compound is a linearalumoxane of formula:

wherein the R¹⁷ substituents, the same or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl,C₇-C₂₀-alkylaryl and C₇-C₂₀-arylalkyl radicals, optionally containing Sior Ge atoms; and t is an integer ranging from 0 to 40 and R¹⁷ has themeaning reported above; or cyclic alumoxanes having formula:

wherein t is an integer ranging from 2 to 40 and R¹⁷ has the meaningreported above.
 11. Catalysts according to claim 10 in which thealumoxane, possibly mixed with the organometallic compounds of aluminiumis used in quantities such as to have molar ratios Al/transition metalcompound greater than
 2. 12. Catalysts according to claim 11, in whichthe molar ratio Al/transition metal compound is between 10:1 and 5000:1.13. Process for the preparation of a solid component according to claim1, comprising (a) dispersing a homogeneous transition metal compound asdefined in claim 1, in a hydrocarbon matrix having a melting point above70° C. which has been brought in a liquid form and (b) solidifying thesaid matrix, containing the said transition metal compound, in the formof spherical particles.
 14. Process according to claim 13, in whichmatrix in liquid form containing the transition metal compound issprayed under conditions of temperature such as to cause solidificationof the droplets in the form of spherical particles.
 15. Processaccording to claim 13, in which the transition metal compound, beforebeing dispersed in the matrix, is dissolved with a minimum quantity ofsolvent.
 16. Process according to claim 15, in which the solvent is ahydrocarbon solvent having a boiling point at atmospheric pressure ofless than 120° C.
 17. Process according to claim 13, in which thetransition metal compound is dissolved together with an activatorcompound.
 18. Process according to claim 17, in which the activatorcompound is a linear alumoxane as defined in claim
 10. 19. Process forthe (co)polymerization of olefins selected from the group comprisingolefins of formula RCH═CHR in which R is independently selected fromhydrogen or a hydrocarbon group with 1-10 carbon atoms, characterized inthat the said process is carried out in the presence of a catalyst asdefined in claim 8.